This invention relates to a motor vehicle inflatable restraint system, and more particularly to a system and method for detecting an out-of-position occupant.
Vehicle occupant position detection systems are useful in connection with air bags and other pyrotechnically deployed restraints as a means of judging whether, and/or how forcefully, to deploy the restraint. Ideally, the system should be capable of classifying the type of occupant (i.e., large adult, small adult, child, etc.) and the position of the occupant relative to the point of deployment of the air bag. Various systems incorporating one or more infrared and/or acoustical ranging sensors have been proposed for this purpose; see, for example, the U.S. Pat. Nos. 5,330,226, 5,785,347, 5,737,083 and 6,113,137. In general, such systems emit one or more beams of infrared energy to define a corresponding number of viewing fields, and detect the received energy to determine occupant presence and position within the viewing fields. Unfortunately, such systems tend to be quite costly, and are difficult to package in the automotive environment. Moreover, a relatively high speed of response is required so that deployment can be properly inhibited or allowed when the occupant position quickly changes, possibly in anticipation of an impending collision. Accordingly, what is needed is a low-cost system that accurately and occupant position quickly changes, possibly in anticipation of an impending collision. Accordingly, what is needed is a low-cost system that accurately and quickly characterizes occupant intrusion into a defined out-of-position area for purposes of deciding whether, or how forcefully, to deploy an inflatable restraint in the event of a serious crash.
The object of this invention is directed to an improved infrared (IR) occupant detection system that is low in cost, and provides accurate and reliable occupant intrusion information at a speed sufficient to timely inhibit or otherwise control deployment of occupant restraints. An array of IR emitters is selectively activated to emit a predetermined pattern of IR beams in an area between the passenger seat and the point of deployment of the restraint, and the reflected IR energy is detected by a photo-sensitive receiver and analyzed to determine whether an occupant is out of position for deployment of the restraint. In the preferred embodiment, the intensity of the received beam energy and the position of the respective beam are used to construct a table of individual intrusion factors, and a composite intrusion factor based on the individual intrusion factors is categorized by magnitude to form an indication of occupant intrusion level, which in turn, is used to determine whether, or how forcefully, to deploy the restraint in the event of a serious crash.